Field of the Invention
The present invention is broadly concerned with improved apparatus for the injection of plural fluids into extrusion system processing components, such as preconditioners and extruders. More particularly, the invention is concerned with such apparatus, alone or in combination with extrusion system processing components, which include injector valves, preferably with interconnected static mixer sections, to efficiently inject steam/water mixtures (and other optional fluids, if desired) using greatly simplified equipment.
Description of the Prior Art
Extrusion cooking systems have long been used for the processing of various types of comestible products, such as human foods or animal feed. Such systems have a number of different components, but the principal processing components are an upstream product preconditioner coupled to a downstream extruder. In the preconditioner, initially dry ingredients are typically mixed with water and/or steam and oil in order to moisturize and partially pre-cook the ingredients. The preconditioned products are then fed into the extruder where the materials are subjected to increasing levels of temperature, pressure, and shear, and are extruded from restricted orifice die structure. In some instances, additional steam and/or water is injected into the extruder barrel during processing, as an extrusion aid and to facilitate complete cooking and forming of final products.
Conventional preconditioners generally include an elongated vessel or housing having one or two elongated, axially rotatable shafts therein having outwardly extending mixing elements or beaters thereon. As the ingredients are advanced toward the outlet of the housing, moisture in the form of steam or water is injected at separate locations along the housing length. Consequently, these preconditioners are equipped with corresponding manifolds with injectors leading to the interior of the housing. Moreover, delivery hoses are usually secured to the manifolds for delivery of moisture. This complicated apparatus can be difficult to service and clean, and requires sophisticated manual operator control to assure proper moisturization at the different injection locations. For example, U.S. Pat. No. 7,906,166 illustrates multiple-injector moisturization apparatus secured to a preconditioner housing. In other cases, additional such assemblies are used for injection along virtually the entire length of the preconditioner housing.
These conventional preconditioners tend to generate and vent a significant quantity of steam during use thereof. This is a serious problem for processors, owing to the fact that this escaping hot steam can readily mix with food particulates, creating a contamination problem as the materials coat the extrusion system components and the adjacent environment. This contamination is aesthetically unpleasant, and can create serious microbiological contamination problems as well. Moreover, the evolution of excess steam is a very inefficient waste of thermal energy.
The injectors used with typical preconditioners are of relatively small diameter, usually on the order of one-half-five-eighths inch, and can have relatively long lengths of over 6 inches. As such, it is quite common for the injectors to become partially or completely plugged during operation of the preconditioners, requiring down time and maintenance/cleanup.
Many of these problems are duplicated where extruders are equipped with conventional injectors, although not usually to the same extent as preconditioners. Nonetheless, it can be difficult to control and continuously operate an extruder where injection/contamination issues are faced.
There is accordingly a need in the art for improved injection apparatus which can be used with preconditioners and/or extruders in order to more efficiently inject plural fluids, while minimizing the plugging and contamination problems endemic with conventional extrusion systems, while optimizing the use of thermal energy.